Apprentice host and former Labour peer Lord Sugar has launched a blistering attack on the party's front-runner to be London mayor, Sadiq Khan.

The billionaire businessman accused Mr Khan of being personally responsible for wrecking the Labour Party as Lord Sugar branded the City Hall favourite and Jeremy Corbyn the "Laurel and Hardy" of politics.

Lord Sugar, who quit Labour to become a non-affiliated peer in protest at what he called its anti-business stance under Ed Miliband, warned Mr Khan would be a disaster for London if he wins the May 5 showdown with Tory Zac Goldsmith.

Labour now welcomes anti-Semites and terrorist sympathisers to its ranks, the TV star warned.

"I would say Khan has single-handedly wrecked the Labour Party, and now he's turning his finely honed judgment on the great city of London," the peer wrote in The Sunday Times.

"Khan ran Ed Miliband's leadership campaign. He was in the room when Miliband turned on people like me, attacking the country's largest employers as 'predators', as well as Corbyn who famously called Britain's businesses the real enemy.

"Khan was one of the most senior Labour politicians to nominate Corbyn for leader. Without Khan's endorsement, Corbyn would never have made it onto the ballot.

"Under Corbyn, the lunatics have truly taken over the asylum. His ambition is to drag Britain back to the 1970s - union blackmail and three-day weeks, when our best and brightest were leaving the country in droves. Militants, Trots, anti-Semites and terrorist sympathisers all seem to have been welcomed into Labour with open arms," the peer said.

Lord Sugar said Mr Khan will not be independent of the Labour leader, as he accused Mr Corbyn of being on friendly terms with terror groups like Hamas.

"No one should be fooled by Khan's stance that he will be totally independent as mayor of London and not influenced by Corbyn. Amazingly, despite the crazy plans to print money to pay for public spending, the Christmas-card list that includes Hamas and the IRA, Khan says he has no regrets about giving Corbyn the top job.

"Be under no illusion, they are two peas in a pod. Clearly not the dynamic duo of Batman and Robin; more like Laurel and Hardy," the peer said.

Lord Sugar said Mr Khan should not get to City Hall just because he peddles a "sob story" about his humble beginnings.

"Maybe I'm missing the point. As far as I can tell, Khan's main offer to London voters isn't his policies; it's that he's the Muslim son of a bus driver. Ok the boy's done good - well done!

"I myself am a working-class Jewish boy from the East End; the son of a factory tailor who never knew where his next day of work was coming from. But that was not a reason why people invested in me and my public companies," the peer said.